Motor fuel solvent additive for increasing engine cleanliness



MOTOR FUEL SOLVENT ADDITIVE FOR IN CREAS- ING ENGINE CLEANLINESS John J. Kolfenbach and John 0. Smith, In, North Plainfield, N.J., assignors to Esso Researchand Engineering Company, 'a-corporation of Delaware No Drawing, Filed Aug, 12, 19s.1,, s r.Neatly-151.

8 Claims. c1. 44-74.)

This invention relates to improvements in motor'filels and particularly to solvent additives for such fuels for the purpose of ensuringengine cleanliness. In particular, the-invention concerns solvent additives that, act, to remove varnish deposits from, or prevent varnishformation on, the moving parts associated with the combustion chamber of an internal combustion engine.

In the operation of a piston engine, a considerable amount of varnish is formed on the piston, cylinder and valve stems. This varnish has an adverse effect upon heat transfer, raises combustion chamber temperatures, increases knocking tendencies (raises octane requirement), and causes valve sticking. It also increases ring sticking tendencies, wear, and oil consumption. A con-' siderable improvement in performance could be realized it this varnish could be prevented from forming or at least accumulating.

It is the principal object of the present invention to provide a combination solvent additive and a motor fuel containing that additive that will prevent the accumulation of varnish and related deleterious deposits in the combustion chamber and on the moving parts of an internal combustion engine. This object is accomplished by employing in the motor fuel a high boiling solvent mixture that will remain in the liquid state in the com bustion chamber for a sufiicient period of time to dissolve varnish as it is formed and to carry it into the crank case oil.

In accordance with the present invention, mixtures of relatively non-volatile nitro compounds and high boiling alcohols are employed as fuel components to reduce varnish accumulation in internal combustion engines. The high boiling nitro compounds of the present invention comprise nitro paraffin hydrocarbons, and in general, the nitro paraffins that are employed have from 3 to carbon atoms. Suitable nitro parafiins include nitropropane, nitrohexane, nitrocyclohexane and nitroheptane.

The high boiling alcohol component of the additive mixture preferably has from 7 to carbon atoms. Suitable alcohols include lauryl alcohol and benzyl alcohol.-

Particularly preferred are oxo alcohols boiling above 250 F. The oxo alcohols are now well known in the art and are synthesized from olefins by reaction of the latter with carbon monoxide and hydrogen in the presence of a cobalt or iron catalyst in a two-stage process. In the first stage the olefinic material and proper proportions of CO and H are reacted in the presence of the catalyst to furnish a product that consists predominantly of aldehydes. The aldehyde product is hydrogenated in the second stage to furnish the corresponding alcohols.

These alcohols are primarily branch-chain primary alcohols and contain an average of one more carbon atom than the olefinic material from which they are derived.

The proportion of nitro compound to alcohol in the compositions of this invention may range from 4 volumes of nitro compound and 1 of alcohol, to 1 volume of nitro compound and 4 volumes of alcohol. Particularly preferred are mixtures in which the nitro compound and 2,962,365 Patented Nov. 29, 1960 alcohol are 'present in about equal proportions,,e.-g., from about 4.0 to 60%. nitro compound and from about 60% to 40% alcohol. The mixture is employed in the volume :concentrationrangeof about 0.05% to 1%.

The following examples serve to illustrate the. advantages, of, this invention.

EX MP E 1 *Fouled pistonsfrom a test engine were employed to compare'the solvent actionof the additive mixture of the present invention with the solvent action of the individual components of the mixture. One piston was dipped into Z-nitropropane, a second piston was, dipped into a C oxo alcohol, and a third piston was dipped into amixtureof'equal volumes of the aforesaid nitropropane and, alcohol. The latter mixture was found to be far superior to either of the components for dissolving the varnish. With the mixture the, varnish was removed on contact. 'Witheither one of thecornponents alone, much varnish remained even after gentle rubbing for 30 seconds to 1 minute.

EXAMPLE 2 A Chevrolet engine which had completed a standard evaluation test on a motor fuel was disassembled and rated for deposits. After the engine had been rated it was reassembled without cleaning and a fresh charge of motor oil was added to the crankcase. The same fuel was employed as in the previous test run, with the exception that 0.5% nitrocyclohexane and 0.5% tridecyl alcohol by volume were added to the fuel. The dirty engine was run for 5 hours and then taken apart and re-rated. Although the overall cleanliness of the engine was substantially unchanged, the piston skirt varnish deposits were considerably reduced. The numerical data for the varnish ratings appear in Table I.

Table I Piston Skirt Varnish Description Vis'ial Weight, Demerit mg.

This reduction in piston skirt varnish by /3 is remarkable considering that it occurred in 5 hours time and was brought about by the small amount of the nitrocyclohexane-alcohol mixture which found its Way past the pistons and which, furthermore, was diluted with gasoline heavy ends and oil.

It is of course to be understood that the motor fuel compositions of the present invention may contain, in addition to the novel mixture herein disclosed, conventional amounts of the usual gasoline additives such as lead tetraethyl or other anti-knock agents, lead scavenging agents, gum inhibitors, oxidation inhibitors, dyes, rust preventives and the like.

While the present invention has been described with respect to certain specific embodiments thereof, restriction to those specific embodiments is not intended. The scope of the invention is limited only by the appended claims.

What is claimed is:

1. An improved motor fuel composition adapted to minimize varnish formation in internal combustion engines which consists of a gasoline containing from about 0.05% to about 1% by volume of a mixture of a nitroparaffin of from 3 to 10 carbon atoms with a high boiling alcohol of from 7 to 15 carbon atoms, the volume 3 proportion ofnitroparafiin to alcohol in the said mixture being in the range of from 4 to l to l to 4.

2. The motor fuel composition of claim 1 in which saidmixture contains about equal proportions of, the initr'opa'r affin and the alcohol. 1 V 1 3. An improved motor fuel composition consisting of a gasoline containing about 0.5 volume percent'of nitrocyclohexane and about 0.5 volume percent of tridecyl alcohol. a 4. The motor fuel composition of claim 1' wherein said alcohol is an oxo alcohol of from 7 to 15 carbon atoms. 5. The motor fuel composition of claim 1 wherein said 6. A solvent composition forremoving varnish He"- posits from internal combustion engine parts which consists of a mixture of a nitroparafiin of from 3 to 10 caraeeaagacs,

:mixture consists of about equal volume proportions of .nitropropane and a 0, 0x0 alcohol.

bon atoms and a high boiling alcohol of from 7 to 15 carbon atoms, the volume proportion of nitroparaffin to alcohol in the said mixture being in the range of from 4to'lto l to4.

v7. A solvent composition for removing varnish deposits from internal combustion engine parts which consists of about equal volume proportions of nitrocyclohexane and tridecyl alcohol 8. A solvent composition for removing varnish deposits from internal combustion engine parts which consists of about equal proportions'of a C oxo alcohol and Z-nitropropane.

References Cited in the file of this patent UNITED 'sTATEs PATENTS fian e' Feb. 6, 1925 1,546,479 eana July 21, 1925 1,825,358 Lovell et a1. Sept. 29, 1931 1 925948" -H enne'n Aug. 29, 1933 2,188,645 Buffington Jan, 30, 1940 2,339,096 Morgan Jan. 11, 1944 2,350,145 Backofi et a1 May 30, 1944 2,259,804 Sherman Aug. 21, 1956 2 ,7.8I5',6 62 h, jBoyce' Mar. 19, 1957 FOREIGN PATENTS 

1. AN IMPROVED MOTOR FUEL COMPOSITION ADAPTED TO MINIMIZE VARNISH FORMATION IN INTERNAL COMBUSTION ENGINES WHICH CONSISTS OF A GASOLINE CONTIANING FROM ABOUT 0.05% TO ABOUT 1% BY VOLUME OF A MIXTURE OF A NITROPARAFFIN OF FROM 3 TO 10 CARBON ATOMS WITH A HIGH BOILING ALCOHOL OF FROM 7 TO 15 CARBON ATOMS, THE VOLUME PROPORTION OF NITROPARAFFIN TO ALCOHOL IN THE SAID MIXTURE BEING IN THE RANGE OF FROM 4 TO 1 TO 1 TO
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